While there is no strict definition for this group of metals, it usually includes those that are extremely rare. Thus, metals that are labeled "precious" are also considered noble metals (note, however, that noble metals are not necessarily precious metals). There are nine known precious metals - gold, platinum, iridium, palladium, osmium, silver, rhodium, ruthenium, and rhenium. mol-1 Atomic: Oxidation States: 6, 5, 4, 3, 2, 1, -1 Electronegativity: 2.28 (Pauling scale) Atomic Radius: 134 picometre Covalent Radius: 142 7 picometre Ionization Energies: 719.7 kJ.mol-1 (first), 1740 kJ.mol-1 (second), 2997 kJ.mol-1 (third) The principal use of rhodium is as a catalytic converter in automotive vehicles, which reduces the toxicity of engine emissions by converting these into less harmful gases. What makes pure gold especially attractive is its bright yellow color and luster. These characteristics are maintained as gold is chemically unaffected by air or moisture. Here are some of the properties of gold: General: Chemical Symbol: Au Atomic Number: 79 Category (as an element): Transition Metal Group/ Period/ Block (in the Periodic Table): 11/ 6/ d Atomic Weight: 196.966569(4) g. Gold And Silver: The Two Precious Traditional Coinage Metals Four transition metals make up group 11 of the periodic table of elements. All, except one, are considered traditional coinage metals. Qualifying this further, only two of these three traditional coinage metals are considered precious metals. Precious Metal Determinants: Rarity And High Economic Value A metal is considered "precious" if it is rare and is of high economic value. Under these two factors, nine metallic chemical elements qualify as precious metals. These are, in no particular order, gold, palladium, silver, rhodium, iridium, ruthenium, platinum, osmium, and rhenium. Coupled with its resistance to extremely high temperatures, this special characteristic makes iridium ideal for use in certain parts of aircraft engines. It is also alloyed with titanium to make deep-water pipes. Other uses of iridium include the following: 1. Electrical contacts for spark plugs (due to its resistance to arc erosion); 2.
Share This Page